Human apolipoprotein (apo) E has three major isoforms, apoE2, apoE3, and apoE4. It has been established that apoE4 is associated with increased plasma cholesterol levels and higher risk for the development of coronary heart disease. ApoE4 has also been linked to the pathogenesis of Alzheimer's disease. The apoE4 allele is a major risk factor or susceptibility gene associated with approximately 40-65% of cases of sporadic and familial Alzheimer's disease and it increases the occurrence and lowers the age of onset of the disease. In addition, the apoE4 allele is also associated with poor clinical outcome in patients with acute head trauma and stroke.
Currently, the only means of definitively diagnosing AD is by autopsy. The presence in brain tissue of the plaques and tangles that are the hallmarks of AD can only be seen clearly in post-mortem brain samples. In living subjects, diagnosis of AD is at best a “possible” or “probable” AD. Currently available diagnostic tests for AD include neuropsychological tests, which measure memory, problem solving, attention, counting, and language; and brain scans. Complicating the diagnosis of AD is the fact that some of the symptoms, such as memory loss, are also associated with other, unrelated disorders.
There is a need in the art for a diagnostic assay for AD that is more accurate and reliable than current diagnostic methods, and which can be performed on living subjects. The present invention addresses this need.
Literature
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